Allow CURRENT/SESSION_USER to be used in certain commands

Commands such as ALTER USER, ALTER GROUP, ALTER ROLE, GRANT, and the
various ALTER OBJECT / OWNER TO, as well as ad-hoc clauses related to
roles such as the AUTHORIZATION clause of CREATE SCHEMA, the FOR clause
of CREATE USER MAPPING, and the FOR ROLE clause of ALTER DEFAULT
PRIVILEGES can now take the keywords CURRENT_USER and SESSION_USER as
user specifiers in place of an explicit user name.

This commit also fixes some quite ugly handling of special standards-
mandated syntax in CREATE USER MAPPING, which in particular would fail
to work in presence of a role named "current_user".

The special role specifiers PUBLIC and NONE also have more consistent
handling now.

Also take the opportunity to add location tracking to user specifiers.

Authors: Kyotaro Horiguchi.  Heavily reworked by Álvaro Herrera.
Reviewed by: Rushabh Lathia, Adam Brightwell, Marti Raudsepp.

1 files changed, 17 insertions, 4 deletions

diff --git a/src/backend/commands/schemacmds.c b/src/backend/commands/schemacmds.c
index 722142e16ea..c090ed220f8 100644
--- a/src/backend/commands/schemacmds.c
+++ b/src/backend/commands/schemacmds.c
@@ -21,6 +21,7 @@
 #include "catalog/dependency.h"
 #include "catalog/indexing.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_authid.h"
 #include "catalog/objectaccess.h"
 #include "catalog/pg_namespace.h"
 #include "commands/dbcommands.h"
@@ -42,8 +43,7 @@ static void AlterSchemaOwner_internal(HeapTuple tup, Relation rel, Oid newOwnerI
 Oid
 CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString)
 {
-	const char *schemaName = stmt->schemaname;
-	const char *authId = stmt->authid;
+	const char	*schemaName = stmt->schemaname;
 	Oid			namespaceId;
 	OverrideSearchPath *overridePath;
 	List	   *parsetree_list;
@@ -58,11 +58,24 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString)
 	/*
 	 * Who is supposed to own the new schema?
 	 */
-	if (authId)
-		owner_uid = get_role_oid(authId, false);
+	if (stmt->authrole)
+		owner_uid = get_rolespec_oid(stmt->authrole, false);
 	else
 		owner_uid = saved_uid;
 
+	/* fill schema name with the user name if not specified */
+	if (!schemaName)
+	{
+		HeapTuple tuple;
+
+		tuple = SearchSysCache1(AUTHOID, ObjectIdGetDatum(owner_uid));
+		if (!HeapTupleIsValid(tuple))
+			elog(ERROR, "cache lookup failed for role %u", owner_uid);
+		schemaName =
+			pstrdup(NameStr(((Form_pg_authid) GETSTRUCT(tuple))->rolname));
+		ReleaseSysCache(tuple);
+	}
+
 	/*
 	 * To create a schema, must have schema-create privilege on the current
 	 * database and must be able to become the target role (this does not